LoadRDataIfExists.R

library(digest)

LoadRDataIfExists <- function(fn) {
  # Calls _fn_ and caches the result on disk, unless the cache already exists
  #
  # _fn_ should be a function with signature _fn(filename, ...)_
  # If cache file exists and is recent, load data from it.
  # Otherwise call the original function.
  function (filename, ...) {
    param.hash = digest(c(fn, list(...))) # Cache file names depends on params/fn def
    cache.filename <- paste(filename, param.hash, 'RData', sep = '.')
    if (file.exists(cache.filename) & 
          file.info(filename)$mtime <= file.info(cache.filename)$mtime) {
      # .RData exists, we need to load it
      return (readRDS(cache.filename))
    } else { 
      # .RData either doesn't exist or outdated, need to replace it
      result = do.call(fn, c(list(filename), ...))
      saveRDS(result, file = cache.filename)
      return (result)
    }
  }
}

Replaced match.call() with list(...) and use saveRDS/readRDS as per @hadley's suggestion